1. Field of the Invention
The present invention generally relates to the field of water heaters and water heating systems, with emphasis on the tankless variety, and particularly relates to the maintenance of said heaters and systems.
2. Background
Tankless or on-demand water heaters are rapid-response water heaters that represent advances over conventional “tank” water heaters, including energy and space savings.
The major components of a conventional tankless water heater are illustrated with reference to FIG. 1. In the tankless water heater 100, a control module serves to electronically control the operation of the unit. Tankless water heaters have similar make-up whether they are larger units designed to supply hot water to an entire structure such as a home or other building, or whether they are smaller units designed to supply hot water to a limited area such as an individual sink or bathroom shower.
In operation, cold, potable water enters the unit 100 via an input 120 to a valve 130, which may optionally contain an emergency shut-off and diverter feature to divert water from the unit if the unit is in a “lock-out” condition. The “lock-out” condition shuts the unit down to protect it from highly inefficient or unsafe operating conditions. Without diversion of the water source, water from the “hot water” designated piping will not flow in the structure.
A flow sensor 160 senses the flow of water coursing through the supply line (i.e., a demand for hot water has been triggered by turning on a hot water faucet or the like) and sends a signal to the control module 110. In response, the control module 110 activates a heat exchanger 170 for rapid heating of the water, whereupon the heated water exits the unit 100 via an output valve 140 and output 150 (toward the hot water demand site in the structure). A heat sensor 180 monitors the heat exchanger temperature and a water temperature sensor temperature of the water leaving the unit.
If the heat exchanger 170 overheats, the control module 110 causes it to shutdown. Large discrepancies between the heat exchanger temperature and the water temperature immediately leaving the heat exchanger can also indicate inefficient or unsafe operating conditions. Either may cause a “lock-out” condition, which will typically also send a visible error signal viewable via a control panel display (not shown).
“Hard” water (or mineral-rich water) poses challenges to the efficient and safe operation of hot water heaters, as mineral deposits, often in the form of calcium or lime scale build-up attach to both heating surfaces and conduits. And while the greater movement of water in the aggregate of tankless water heaters may lead to a reduction of scale build-up, compared to convention tank units, scale build-up is nonetheless a problem. Scale deposit build-up is observed in tankless water heater units over time even where “softer” potable water is used. Therefore, tankless water heater units need to be periodically descaled for efficient and safe operation. Because of their higher initial costs, it is not economical to discard tankless water heaters with the same frequency as lower-cost tank heaters when scale build-up occurs.
The primary prior art approach to descaling tankless water heaters, is a manually one where a service person decouples the unit from the supply and output lines and forces a descaling cleaning solution through the tankless unit conduits to remove the scale build-up. The cleaning solution and any scale build-up collected in the process are purged from the system. The process is repeated as needed. Unfortunately for tankless water heater unit owners, the manual descaling process can be expensive (for labor costs and the costs attributable to a portion of expensive, special-purpose descaling equipment) and inconvenient, as well as disruptive of hot water peak demand time.
The other prior approach is to install scale inhibition filters that reduce scale build-up. However, this only delays the inevitable by relative slight times, and can be costly over time as well.
The typical tankless water heater unit requires thorough descaling once or twice a year. Thus, there is a long-standing, but unmet and unsolved need to provide tankless water heaters and tankless water heating systems that do not require labor-intensive descaling, as the prior art uniformly teaches and suggests labor-intensive descaling approaches. There is also a long-standing, but unmet and unsolved need to meaningfully reduce descaling costs over the life of tankless water heaters and tankless water heating systems.